Genetic Information, Variation and relationship

• What is a gene?

  A section of DNA located at a particular site on a DNA molecule called its locus
• What carries the genetic code that determines the sequence of amino acids during protein synthesis?

  The base sequence of each gene
• The genetic code is ..................... in all organisms, providing indirect evidence for evaluation

  The same
• What can genetic diversity within a species be caused by? (3)

  Gene mutation, chromosome mutation, random factors associated with meiosis and fertilisation
• Variation within a species can be measured using..........

  Differences in the base sequence of DNA or in the amino acid sequence of proteins
• How can biodiversity within a community be measured?

  Using species richness and an index of diversity
• What are prokaryotes?


  Unicellular organisms that do not develop or differentiate into multicellular forms
• Some bacteria grow in ...................... or ..................... of cells but each cell in the colony is .................. and .................. of independent existence.

  Filaments

  Masses

  Identical

  Capable
• ............................ are capable of inhabiting almost every place on the earth

  Prokaryotes
• ..................... have no nuclear membrane

  Prokaryotes
• What does the cytoplasm of a prokaryote contain?

  All enzymes needed by the cell for metabolic reactions.
• Explain the nucleoid of a prokaryote


  The region of the prokaryotic cytoplasm that contains DNA -not surrounded by a nuclear membrane
• Describe the DNA in prokaryotes

  Always circular, it is compacted by a mechanism called supercoiling and is not associated with any proteins.
• Describe the plasmids in a prokaryote


  Small circles of DNA used to exchange DNA between bacterial cells, very useful for genetic engineering
• Describe the mesosome of a prokaryote

  Tightly folded region of the cell membrane containing all the membrane bound proteins required for respiration & photosynthesis
• Describe the cell wall of a prokaryote

  Made of murein which is a glycoprotein
• What are the two types of cell walls in prokaryotes and how can they be distinguished?

  Can be distinguished with gram stain 2 types:

  Gram positive bacteria - thick cell wall which stains purple

  Gram negative bacteria- thin cell wall with an outer lipid layer and stain pink
• Describe the capsule of a prokaryote and what it's used for

  Thick polysaccharide layer outside of cell wall , used for sticking cells together as a food reserve , as protection against desiccation, and chemicals , as protection against phagocytes
• Describe the flagellum and how it works

  A rigid, rotating helical shaped tale used for propulsion. Motor is embedded in cell membrane and is driven by a hydrogen gradient across the membrane. Clockwise drives cell forwards , anti-clockwise causes chaotic spin
• Explain the endosymbiosis idea


  The thought that organelles of eukaryotes such a nuclei, mitochondria and chloroplasts could originally be derived from prokaryotic cells that have become incorporated inside other prokaryotic cells
• Name 5 observations that support the idea of endosymbiosis

  - Organelles, like prokaryotic cells, contain circular dna

  - organelles, like prokaryotic cells, contain 70s ribosomes

  - organelles have double membranes (as though a single cell membrane had been engulfed by another)

  - organelles reproduce like prokaryotic cells by binary fission

  - organelles are like some bacteria that are alive today
• What is the major difference between prokaryotes and eukaryotes?

  Eukaryotes cells contain membrane bound compartments where specific metabolic activity takes place , most importantly the nucleus
• In the nucleus, dna molecules are very long, linear and associated with proteins called.....

  Histones
• Together, a dna molecule and it's associated proteins form a ......

  Chromosome
• What are exons and introns?

  Exons are a coding base sequence for amino acids

  Introns are non coding sequence that separates exons
• What are responsible for production of certain enzymes and proteins that are needed to produce a characteristic?

  The sequences of nucleotide bases that make up a gene
• What are alleles?


  Different versions of the same gene
• What is a cistron?

  A sequence of bases that is equivalent to one gene
• What is the locus?


  where the gene is located on the chromosome
• What is a codon?


  A sequence of 3 dna bases that codes for an amino acid
• How many amino acids is dna capable of coding for?

  64
• How many amino acids are there?

  20
• Some .............. ............ have more than ........... combination of .............. coding for them

  Amino acids

  One

  Bases
• What is a stop and start codon?

  A codon at the end or beginning of a polypeptide
• What is universal, non overlapping and degenerate?

  The genetic code